Irruptive Behavior?

Lewis’s Woodpecker

Although Lewis’s woodpeckers (Melenerpes lewis) are not overly abundant here in Northeastern California, Leonard and I usually saw them several times each year. We eventually learned a few areas where they could usually be found. However, in the last couple years we did not see any local Lewis’s woodpeckers and wondered why. Had their range changed for some climatic reason? Did a disease affect the population? Did we simply miss sighting them? Where were the Lewis’s woodpeckers?

About two weeks ago while hiking the Loop Trail at Baum Lake (Shasta County CA) we saw at least ten Lewis’s woodpeckers congregating near a ponderosa pine snag. How exciting? Since then, we returned twice and both times saw Lewis’s woodpeckers, both at the snag and at other locations near the lake. Why were we suddenly seeing these “missing” woodpeckers.

Lewis’s woodpeckers are beautiful birds with their glossy, greenish-black upper parts, pale grey breast band and collar, pinkish belly and deep red face. They inhabit open pine woods or areas with scattered trees and shrubs west of the Great Plains. Short-distance migrants, Lewis’s woodpeckers move to lower elevations and lower latitudes in the winter. Where we live Lewis’s woodpeckers are resident, only leaving briefly during severe winter conditions. In the spring and summer Lewis’s woodpeckers feed mainly on insects which they primarily catch while in flight. In the winter, their diet consists of acorns and conifer or other seeds.

Lewis’s woodpeckers are irruptive species. (Irruption is associated with sporadic or unpredictable food supplies resulting in birds migrating to widely separated areas in different years.) Their movements in the winter are irregular depending on the availability of acorns or seeds. Although there always seemed to be abundant supplies of acorns, maybe the “disappearance” of the Lewis’s woodpecker for several years was related somehow to food supply.

Leonard and I will probably never know why we missed observing Lewis’s woodpeckers for about two years. Whatever the reason, we are happy they have returned.





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2 Responses to Irruptive Behavior?

  1. Lin Erickson says:

    That IS exciting, Chris! Now maybe I can see one this summer.

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